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Assessment of road noise at long distances from the source; a comparison between measurements and sound prediction models evaluating the effects of noise barriers
No full textPredicting how sound propagates from road traffic noise is essential for environmental
noise assessments and for designing effective mitigation strategies. However,
the accuracy of current theoretical models tends to become more uncertain as the
distance from the source increases, especially when factors such as vehicle speed,
traffic volume, and terrain complexity increase, or when noise barriers are introduced.
Although there has been research on long-distance sound propagation, few
studies have examined the differences between predicted and measured sound levels
beyond 150 meters, particularly in cases where noise barriers are involved.
This thesis investigates discrepancies between theoretical predictions and short-term
field measurements of road noise at distances ranging from 180 to 350 meters, both
with and without noise barriers. Sound levels predicted by two commonly used models,
Nord2000 and CNOSSOS-EU, were compared against measurement data from
four locations with varying terrain conditions. These were short-term measurements
(1-3h) that followed the NT ACO 0039 standard. Additionally, a simpler prediction
model was developed in MATLAB using standard calculation formulas to assess its
performance against the more complex models.
The results show consistent discrepancies between predicted and measured values,
particularly in complex terrain. Nord2000 achieved the closest agreement, with
RMSE values around 3.3–4.1 dBA, while CNOSSOS-EU showed slightly higher deviations
of 3.7–4.5 dBA. These error levels are consistent with previous studies and
may be interpreted as indicative of model prediction uncertainty. The inclusion of
noise barriers appeared to increase prediction errors. However, further data collection
is necessary before drawing statistically significant conclusions.
Understanding how noise propagates over long distances is key in order to evaluate
the reliability of prediction models. Continued research is needed to strengthen
confidence in noise assessments at extended range
A Chalmers University of Technology Conceptional Design Method for Propellers. An implementation of Drela method for minimum induced loss and Garrick and Watkins method for sound pressure level
No full textThe ongoing development of electric aircraft aims to make the aviation industry more sustainable, with a focus on reducing energy consumption and noise emissions. Propellers, as a key component of electric airplanes, play a critical role in achieving these goals. This study focuses on designing optimized propellers for electric aircraft that maximize efficiency while minimizing energy loss and sound pressure levels (SPL). By employing Drela’s propeller design methodology for aerodynamic optimization and Garrick and Watkins models for noise analysis.
The primary tool used in this study is OptoProp, a numerical simulation program developed in Python to optimize propeller efficiency. The methodology involves several key steps. First, the program is verified using a documented case to ensure its accuracy in predicting propeller performance. Following verification, a parameter sensitivity study is conducted to understand how critical design elements, such as blade count, diameter, and angular speed, influence efficiency and noise levels. The final step involves conducting noise simulations using the calculated aerodynamic data to analyze the relationship between propeller parameters and SPL, providing deeper insight into the effects of each parameter.
The results of the parameter study reveal several important trends. The propeller’s diameter and blade count are pivotal in determining its overall efficiency. A larger propeller size enhances efficiency by reducing the power required and lowering the generated torque, both of which are critical for achieving sustainable performance.
However, increasing the diameter also leads to a positive effect on SPL, as larger propellers tend to produce less noise due to their inverse relationship with the sound pressure level. While this trend offers a valuable approach to designing propellers with better performance and reduced noise levels, there is a threshold for both the diameter and blade count. Beyond this threshold, further increases in these parameters have detrimental effects on performance and can lead to suboptimal propeller designs. This suggests that simply increasing the size or number of blades does not always result in improved performance, and a balanced design is essential.
On the other hand, the effect of angular speed on propeller performance is also significant. Increasing the angular speed improves efficiency up to a certain optimal value, after which further increases yield diminishing returns. However, angular speed has a negative impact on SPL, meaning that higher speeds generate more noise. This introduces a critical trade-off between performance and noise, as designers must be cautious not to increase the angular speed beyond the optimal level if low noise levels are a priority. The sensitivity of noise to angular speed makes it an important factor in designing propellers for electric aircraft, where minimizing noise
pollution is a key concern.
In conclusion, the study provides valuable guidelines for designing electric aircraft propellers that balance high aerodynamic performance with low noise emissions. The findings suggest that an optimal propeller design must consider not only aerodynamic
efficiency but also the impact of various parameters on SPL. The balance between propeller size, blade count, and angular speed is crucial for achieving sustainable performance, with thresholds for each parameter that must be respected to avoid diminishing returns in both efficiency and noise reduction. These insights contribute to the development of electric aircraft technology and offer a pathway
toward more sustainable aviation solutions, where both environmental impact and noise pollution are minimized without compromising on performance
Mechanical performance and material characterization of secondary aluminum alloys for automotive megacasting
No full textThe transition toward sustainable automotive manufacturing has intensified interest
in using recycled materials without compromising mechanical performance. This
thesis investigates the feasibility of applying secondary aluminum alloys in highpressure
die casting (HPDC), specifically within the megacasting process for large
structural components. Four alloy batches were analyzed: one primary aluminum
used as the reference (A4), one secondary aluminum with similar chemical composition
(B1), and two secondary aluminum variants with different levels of Fe, Cu, Zn,
and V (B2–B3). Mechanical performance was evaluated through tensile, three-point
bending, and hardness testing, while microstructural analysis, including optical microscopy,
metallography, SEM, and X-ray was used to identify shrinkage, porosity,
and intermetallic phases.
The results show that recycled aluminum with up to 90% secondary content (B1) can
achieve comparable mechanical properties to primary aluminum (A4) when chemical
composition remains unchanged. Batches with higher Fe content (B2, B3) exhibited
increased yield strength due to solid solution and precipitation strengthening but
showed reduced ductility and bending toughness, particularly in regions with greater
shrinkage. Comparing the results with historical trials can separate the impact of
cast processing and raw material. Microstructural analysis confirmed that casting
position influences defect formation and performance. In HPDC, areas farther from
the ingate (e.g. F3) generally experience longer flow paths and therefore tend to
form more shrinkage and intermetallic phases. Building on this context, this work
demonstrates that, with optimized chemistry and process parameters, secondary
aluminum alloys can achieve mechanical performance compared with primary alloys,
thereby offering a sustainable megacasting solution for the automotive industry
Measuring and modeling material properties during high loading rates - Material characterization of A36 steel under high loading rates using the Split Hopkinson Pressure Bar and numerical modeling
No full textThis thesis aims to evaluate a method for analyzing the high strain rate behavior of A36 steel by combining experimental testing and numerical modeling. Experiments consisting of uniaxial compressive tests and Split Hopkinson Pressure bar tests were performed to cover low and high strain rates. The method’s ability to use low strain rate data to predict high strain rate behavior using the Johnson-Cook material model was evaluated. Numerical modeling and parameter optimization were performed in LS-DYNA and LS-OPT, respectively. The results showed reasonable agreement between the experiments and simulations for hydraulic compressive and Split Hopkinson Pressure Bar tests. Consistently, an explicit strain rate dependency is present throughout the tests, but fluctuations in the Split Hopkinson Pressure Bar data complicated the data analysis. The method has strengths and limitations. While the Johnson-Cook material model effectively models A36 steel at high strain rates, additional refinements in the numerical model and parameter optimization process are needed to obtain a reliable set of parameter values. Improving the reliability of the strain gauge data and introducing striker velocity measurements could elevate future method development. In this thesis, the method chosen to evaluate steel’s high strain rate behavior provides a foundation for further work. Refinements in experimental setup and numerical modeling are necessary to improve the reliability of the results before they can be applied effectively in future studies
Pisa - Facilitating conjecture generation in Lean
No full textAs time has passed, the rigour needed for mathematical proofs has increased. Interactive theorem provers were introduced to help with proof verification during proof development. This project aims to aid users while they use a particular interactive theorem prover, known as Lean 4, by facilitating the use of conjecture generation for the language. Conjecture generation can help users understand the domain that they are working in, or automate what proofs might be needed for a more intricate proof. To facilitate conjecture generation in Lean, a tool called Pisa was introduced. It utilizes tooling from Haskell to generate conjectures. To be able to utilize Haskell tooling for conjecture generation, a translation from Lean to Haskell was created, that supports data type translation and has an interpreter for functions. The translation works for enumerable, recursive, and polymorphic data types. With the translation, generation of conjectures is performed and then translated back into Lean code for the user to prove them. This was all tied into a macro, that is callable from the users’ editor, meaning that usage of Pisa can be done while adding and modifying definitions
Digitalization and model-based construction in Sweden: Evaluating competitiveness within the consultant industry
No full textByggbranschen står inför utmaningar vad gäller innovation och effektivitet jämfört
med andra branscher. Det svenska behovet av byggnation, både av infrastruktur och
bostäder, är stort inom en snar framtid. Building Information Modeling (BIM) har
ökat under de senaste decennierna, där modulbaserat byggande är ett kärnan för att
öka produktiviteten i de olika byggfaserna. BIM fungerar som en informationshubb
där komponenter i byggnationen innehåller nödvändig information istället för att
enbart utgöra en visuell modell. Processens samarbete kan öka, beslut i designfasen
kan fattas med precision och förvaltning av fastigheter kan ske mer effektivt. Detta är
ett av de områden där digitalisering påverkar hela branschen och något som
intressenter kan dra nytta av. Att skapa en stad eller miljö där byggnation sker med
högre produktivitet kan påverka flera parametrar såsom miljöpåverkan, kostnader för
invånare och lägre kostnader kopplat till service.
Syftet med examensarbetet är att utvärdera vilka incitament olika beställare och
fastighetsägare har för att beställa en digital projektleverans med BIM, istället för
traditionella projektleveranser. Vidare tas konsultperspektivet för att undersöka hur
konsultföretag kan arbeta med kunskapshantering och hur deras organisation kan
positionera sig för framtida möjligheter inom digitalisering. Metoden för
informationsinsamling är abduktiv och kombinerar en enkät med semistrukturerade
intervjuer med experter och ledare inom AEC-branschen.
Sammanfattningsvis påvisar examensarbetet fördelar med BIM ur olika perspektiv,
med angivna incitament för dess implementering. Ökat samarbete med
kostnadseffektiva lösningar ger konkurrensfördelar för många olika intressenter inom
sektorn. Slutligen ges rekommendationer till olika intressenter såsom beställare och
konsultföretag i syfte att leda förändringen mot digitalisering och BIM implementering inom byggsektorn
Adoption of Voice User Interfaces in Controlling In-Vehicle Features, Understanding Key Influencing Factors and Creating Design Guidelines for Replacing Physical Controls
No full textContemporary vehicles are usually equipped with numerous interior features with complicated designs, which usually results in higher energy consumption, safety issues related to distractions, and a shorter service life due to the overreliance on screens and complicated interfaces. To address this issue, it is necessary to develop a concept to reduce the number of interior
features. The purpose of this thesis is to investigate whether the VUI (voice user interface) has the ability to replace the physical controls in operating driving task during driving. Three research questions guide this investigation. The literature review employs Desmet’s Product Emotion and Experience theories as a foundation for understanding VUI, alongside an analysis of the current state of VUI research. A mixed-method approach was used to explore user perspectives, incorporating qualitative and quantitative data collected through questionnaires, interviews, and statistical analysis. The findings reveal that participants expressed a more positive attitude toward using VUI for secondary and tertiary driving tasks, while showing reluctance for primary driving tasks. Based on these insights, a User Perception Mechanism and a Decision-Making Model were developed, accompanied by design guidelines. A comparative experimental study identified specific physical controls that could be replaced by voice interaction. These findings informed the creation of use scenarios and the development of a concept —a car key fob inte grated with VUI, which was visualized with 3D design tools. The results suggest that VUI has significant potential to support controlling driving tasks features, enhance user experience, and contribute to the development of future intelligent car cockpits
Tolerance Simulation Optimization with Data Analysis
No full textThis thesis study primarily focuses on simulation chain accuracy through data-driven
optimization techniques within the BIW (Body In White) assembly. Geometry
assurance plays an important role in maintaining the quality throughout the product’s
lifecycle by managing the deviations that originate from manufacturing and assembly
processes. In complex assembly scenarios, especially within BIW Assembly that
involves mixed materials and varying structural rigidity, the simulation accuracy
becomes challenging, and it requires a better understanding of existing models. The
primary objective is to refine the simulation models that predict geometric variations
to enhance the predictive capability. To achieve the objective, a detailed correlation
study has been conducted, analyzing and comparing the real-world measurement
data with rigid and non-rigid simulation models, assessing the effects, like process
adjustments.
The comparison study between the production data and tolerance simulation model
data is used to derive root cause analysis within each sub-assembly. Based on this
study, improvements were made within existing rigid simulation models and suggested
optimized simulation guidelines. This research aspires to find the major contributors to
the geometrical variations within the BIW Upper body assembly and also to bridge the
gap between simulation models and real-world data, improving the robustness within
the rigid body simulation
The local; design informed by local materials and place
No full textIn a globalised world, where most things we interact
with are international in one way or another, from
companies and brands to architecture and design,
finding what’s specific and local gets increasingly
harder. The sense of place and its identity are
gradually getting diluted in this context. In contrast
to this fluid world physical materials can be seen as
absolute with their characteristics strongly linked to
its origin. The materials used when creating spaces
are essential, together with form they make up the
cornerstones of what we experience. Building on the
notion that materials can express a connection to its
context, an understanding of an areas resources and
what role they have played and how they have been
used before could provide a framework for designing
in the future, allowing additions to set side by side
with its context, contributing to the local character.
The question explored in this thesis is how a
design proposal for a swimminghall in the region of
Jämtland can be informed by local materials.
The project consists of three parts; theoretical
studies, context analysis and design iterations. By
exploring the potential use of local materials, in
relation to the concept of identity, combined with
theories of critical regionalism, this thesis aims to
synthesize these elements into a design that builds
upon its material context in a contemporary way
without turning to historical imitation. Highlighting
the importance of the characteristic and influential
buildings in the urban fabric. How a few buildings
of strong character can act as the carrier of local
identity, thereby helping people to navigate and feel
closeness to the surroundings, strengthen the sense
of place.
The Project is situated in Östersund, on the
waterfront of Storsjön. The city was in need of a new
swimming facility, after the old one was condemned
beyond renovation. At the same time Storsjöstrand
was being transformed from an industrial area within
the city to an urban district. Through the public
program of a swimminghall, the project aims to serve
as a node and magnet, activating the new area by
inviting and drawing the public to the waterfront